Project (1) seeks to apply systems analysis (both linear and nonlinear) to characterize the response properties of neurons that fire repetitively. Combined with ion substitution and use of chemical 'dissectors', an attempt is being made to define the ionic mechanisms that underlie repetitive firing and to examine the consequences of the nonlinearities in the encoder output from the standpoint of information processing. Project (2) seeks to examine the influence of intensity-modulated, monochromatic light on the output of opponent-color-coded ganglion cells in the vertebrate retina. An attempt will be made to synthesize an overall transfer function for these cells in terms of the spectral composition of input light, time-varying modulation of the light intensity, and performance of the encoder portion of the cell in producing impulse trains.